My question is about protecting the analog input pins on an Arduino Mega from over voltage. I've seen many topics on this, and the zener diode solutions are typically outlined. These are good solutions. http://www.thebox.myzen.co.uk/Tutorial/Protection.html
However, my question is this: If I am always getting my 5V reference from the Arduino 5V pins, would over voltage protection be of any benefit? For example, I may wish to generate a 0-5V voltage from a pot, by connecting on leg of the pot to 5V (from the arduino), GND, and have the wiper go to an analog input pin. In this case, it would seem that input protection on the analog pins would add no benefit. After all, if the 5V (which came from the Arduino board itself) surges, the Arduino itself is cooked.
Also, I may want to connect an absolute encoder to an analog input. Again, the encoder needs to be hooked up to 5V. And if that 5V comes from the Arduino, transient suppressing circuitry or over voltage circuitry would seem redundant.
Are my assumptions sound?